861cf344575acd50ed67b35d88615f2318610d8148e8c471ad10ca0132cda91eEmpirically, far from isolating a microeconomic core, real-business-cycle models, as with other representative-agent models, use macroeconomic aggregates for their testing and estimation. Thus, to the degree that such models are successful in explaining empirical phenomena, they point to the ontological centrality of macroeconomic and not to microeconomic entities … At the empirical level, even the new classical representative-agent models are fundamentally macroeconomic in content …

The nature of microeconomics and macroeconomics — as they are currently practised​ — undermines the prospects for a reduction of macroeconomics to microeconomics. Both microeconomics and macroeconomics must refer to irreducible macroeconomic entities.

Kevin Hoover

Kevin Hoover has been writing on microfoundations for more than 25 years, and is beyond any doubts the one economist/econometrician/methodologist who has thought most on the issue. It’s always interesting to compare his qualified and methodologically founded assessment on the representative-agent-rational-expectations microfoundationalist program with the more or less apologetic views of freshwater economists like Robert Lucas:

hoovGiven what we know about representative-agent models, there is not the slightest reason for us to think that the conditions under which they should work are fulfilled. The claim that representative-agent models provide microfoundation​s succeeds only when we steadfastly avoid the fact that representative-agent models are just as aggregative as old-fashioned Keynesian macroeconometric models. They do not solve the problem of aggregation; rather they assume that it can be ignored. While they appear to use the mathematics of macroeconomics​, the subjects to which they apply that microeconomics are aggregates that do not belong to any agent. There is no agent who maximizes a utility function that represents the whole economy subject to a budget constraint that takes GDP as its limiting quantity. This is the simulacrum of microeconomics, not the genuine article …

[W]e should conclude that what happens to the microeconomy is relevant to the macroeconomy but that macroeconomics has its own modes of analysis … [I]t is almost certain that macroeconomics cannot be euthanized or eliminated. It shall remain necessary for the serious economist to switch back and forth between microeconomics and a relatively autonomous macroeconomics depending upon the problem in hand.

Instead of just methodologically sleepwalking into their models, modern followers of the Lucasian microfoundational program ought to do some reflection and at least try to come up with a sound methodological justification for their position. Just looking the other way won’t do. Writes Hoover:

garciaThe representative-­agent program elevates the claims of microeconomics in some version or other to the utmost importance, while at the same time not acknowledging that the very microeconomic theory it privileges undermines, in the guise of the Sonnenschein-­Debreu­-Mantel theorem, the likelihood that the utility function of the representative agent will be any direct analogue of a plausible utility function for an individual agent … The new classicals treat [the difficulties posed by aggregation] as a non-issue, showing no appreciation​ of the theoretical work on aggregation and apparently unaware that earlier uses of the representative-agent model had achieved consistencywith​h theory only at the price of empirical relevance.

Where ‘New Keynesian’ and New Classical economists think that they can rigorously deduce the aggregate effects of (representative) actors with their reductionist microfoundational methodology, they — as argued in my On the use and misuse of theories and models in economics — have to put a blind eye on the emergent properties that characterize all open social and economic systems. The interaction between animal spirits, trust, confidence, institutions, etc., cannot be deduced or reduced to a question answerable on the individual level. Macroeconomic structures and phenomena have to be analyzed also on their own terms.